Ink, ink jet recording method, recording unit, ink cartridge, and ink jet recording apparatus

ABSTRACT

An ink jet ink contains at least a coloring material and a specific water-soluble organic solvent and has both excellent color developability and excellent humidity resistance. The coloring material exhibits a small (9 or less) color difference ΔE value which is determined by a method including a series of specific steps and is represented as the square root of (L 1 -L 2 ) 2 +(a 1 -a 2 ) 2 +(b 1 -b 2 ) 2 . The specific water-soluble organic solvent has an evaporation rate X smaller than that of water and a moisture absorptivity Y, the values of X and Y satisfying the relation of Y≦2.8X+10. The content of the specific water-soluble organic solvent is 50 mass % or more of the total amount of water-soluble organic solvents contained in the ink.

This application is a continuation of International Application No.PCT/JP2005/012701, filed Jul. 4, 2005, which claims the benefit ofJapanese Patent Application Nos. 2004-196446 filed Jul. 2, 2004,2004-196449 filed Jul. 2, 2004 and 2005-193806 filed Jul. 1, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet ink having good colordevelopability, good humidity resistance, and high reliability as inkjet ink; an ink jet recording method; a recording unit; an inkcartridge; and an ink jet recording apparatus.

2. Related Background Art

An ink jet recording method is a recording method involving applying asmall ink droplet to any one of recording media such as plain paper andglossy media to form an image, and has become rapidly widespread owingto a reduction in its cost and an improvement in its recording rate.With the rapid spread of a digital camera in addition to an improvementin quality of an image recorded by the method, the method has beengenerally used as a method of outputting a photographic image comparableto silver halide photograph.

In recent years, image quality has undergone improvement more than everowing to, for example, extreme reduction in size of an ink droplet andan improvement of the color gamut involved in the introduction ofmulti-color ink. Meanwhile, there have been growing demands for acoloring material and ink, and stricter properties have been required interms of an improvement of color developability and reliability such assticking property or ejection stability.

As compared to silver halide photograph, the ink jet recording method isproblematic in terms of, for example, the image storage stability of theresultant recorded article. In general, the recorded article obtained bymeans of the ink jet recording method is inferior in image storagestability to silver halide photograph, and involves a problem in that acoloring material on the recorded article is apt to deteriorate to causea change in color tone of an image and the color fading of the imagewhen the recorded article is exposed to light, humidity, heat, anenvironmental gas present in the air, or the like for a long period oftime. To solve the problem, a large number of proposals have beenconventionally made.

In general, the ink jet recording method involves the use of inks eachhaving a hue of yellow, magenta, cyan, black, or the like. It has beenheretofore acknowledged that the yellow ink out of the inks must beimproved in light resistance, water resistance, humidity resistance, andthe like. For improving those properties, there has been proposed, forexample, the use of a coloring material having a specific structure suchas C.I. Direct Yellow 173 or C.I. Direct Yellow 86 (see, for example,Japaneese Patent Application Laid-open No. H02-233781 and JapanesePatent Application Laid-open No. H04-233975). The use of such coloringmaterial as mentioned above shows significant improvements of lightresistance, water resistance, and humidity resistance, but, color tone,color developability, reliability, and the like are not at sufficientlevels.

There has also been proposed the use of C.I. Direct Yellow 132 as anyone of a yellow ink and a coloring material for an ink set (see, forexample, Japanese Patent Application Laid-open No. H11-29729 andJapanese Patent Application Laid-open No. 2001-288391). Although thecoloring material has often been used for ink jet ink because of itsgood color developability, the coloring material involves a problem inthat its humidity resistance is remarkably bad.

There have also been proposed the use of a coloring material having aspecific structure to aim at improving humidity resistance (see, forexample, Japanese Patent Application No. H11-217529) and the use of anink set of multiple colors to improve humidity resistance (see, forexample, Japanese Patent Application Laid-open No. H11-180028).

Each of the proposals described above has attempted to improve humidityresistance, but merely depends on the structure of a coloring material.In other words, neither proposal for improving humidity resistance bymeans of a coloring material having a specific structure nor proposalfor improving humidity resistance by means of an ink set of multiplecolors can prevent migration (image deterioration due to a change incolor tone in an environment such as ahigh-temperature-and-high-humidity environment).

There has also been proposed the synthesis of a novel coloring materialhaving humidity resistance, light resistance, water resistance, and ahue and sharpness suitable for ink jet recording (see, for example,Japanese Patent Application Laid-open. 2003-321627) However, even whensuch coloring material is used, a certain ink prescription cannot reachthe level of humidity resistance requested in a current ink jetrecording method in some cases.

SUMMARY OF THE INVENTION

In view of the foregoing background, the inventors of the presentinvention have acknowledged that humidity resistance that is the largestconcern in a coloring material having a yellow hue must be improved, andthat a yellow ink excellent in both color developability and humidityresistance must be prepared.

The inventors of the present invention have found that a coloringmaterial used in a conventional yellow ink for ink jet recording tendsto be poor in humidity resistance when the coloring material has goodcolor developability, while the coloring material tends to be poor incolor developability when the coloring material has good humidityresistance. Such tendency is also in correlation with the molecularweight of the coloring material. In general, a coloring material havinga large molecular weight hardly moves in a recording medium when thecoloring material is brought into contact with excessive humidity afterthe coloring material has been fixed to the recording medium. As aresult, humidity resistance can be improved. Meanwhile, the coloringmaterial having a large molecular weight has a structure in which a partnot contributing to coloring is relatively large, so coloring efficiencyper unit mass reduces. Therefore, when a coloring material having alarge molecular weight and good humidity resistance is to be used, colordevelopability must be sacrificed. In other words, compatibility betweencolor developability and humidity resistance in an ink containing ayellow coloring material must be achieved in order to increase the imagestorage stability of an ink jet recorded article to the level of silverhalide photograph or higher.

The inventors of the present invention have made the followinginvestigation for pursuing the mechanism with which a change in colortone of a recorded article due to migration occurs and for preventingthe migration itself. To be specific, the inventors have madeinvestigation into a specific ink composition a recorded articleobtained from which is found to change its color tone owing tomigration. As a result, the inventors have found that the occurrence ofmigration largely depends on the presence or absence of a specificwater-soluble organic solvent. That is, the inventors have confirmedthat migration occurs when a water-soluble organic solvent remaining ina recorded article absorbs moisture in the air in ahigh-temperature-and-high-humidity environment.

The present invention has been made on the basis of the foregoingfindings, and the inventors of the present invention have paid attentionto an image formed on a recording medium, paid attention to a differencebetween a component of an ink before the image formation and awater-soluble organic solvent component remaining in the recordingmedium after the image formation, and pursued the respective propertiesof a water-soluble organic solvent in the ink. As a result, theinventors of the present invention have found the mechanism with which achange in color tone due to migration occurs from a difference betweenproperties of the water-soluble organic solvent remaining in a recordedarticle. Then, the inventors have judged that a change in color tone dueto migration largely depends on the total amount of a water-solubleorganic solvent remaining in a recorded article and the property withwhich the water-soluble organic solvent substantially contains watermolecules. The inventors have made extensive studies about this point,thereby completing the present invention.

As described above, the inventors of the present invention have foundthat migration is caused by an interaction between the humidityresistance of a coloring material and a water-soluble organic solvent.

Therefore, a major object of the present invention is to provide a noveltechnique for suppressing a change in color tone due to migration bypaying attention to the amount of a water-soluble organic solventpresent in a recorded article on the basis of the foregoing finding.

Another object of the present invention is to provide an ink excellentin humidity resistance and properties as an ink jet ink such as start upejection stability.

Another object of the present invention is to provide an ink excellentin humidity resistance, start up ejection stability, image density, andcolor tone.

The above objects are achieved by the present invention described below.That is, according to one aspect of the present invention, there isprovided an ink jet ink, comprising at least a coloring material andwater-soluble organic solvent, characterized in that the ink jet inksatisfies the following conditions (A) and (B):

(A) A color difference ΔE judged by means of a method of judgingproperties of a coloring material including the following steps (1) to(3) is 9 or less,

(1) A step involving: applying a model ink comprising the coloringmaterial, water, and a water-soluble organic solvent having anevaporation rate X (mass %) smaller than the evaporation rate of waterand a moisture absorptivity Y (mass %) which is 20 or more and satisfiesa relationship of Y≧2.8X+10; and applying a clear ink prepared byreplacing only the coloring material of the model ink with water in sucha manner that the amount of the model ink is smaller than that of theclear ink,

(2) A step involving: leaving a recorded article obtained in the step(1) in an environment having a temperature of 25° C. and a humidity of60% for 48 hours; and subsequently leaving the recorded article in anenvironment having a temperature of 30° C. and a humidity of 80% for 168hours,

(3) A step of judging the color difference (ΔE) represented by thefollowing expression (1) between the recorded article before the leavingfor 168 hours and the recorded article after the leaving for 168 hours,ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}  (1)(In the expression (1), L₁, a₁, and b₁ represent L, a, and b of an Labcalorimetric system after the leaving for 48 hours and before theleaving for 168 hours, respectively, and L₂, a₂, and b₂ represent L, a,and b of the Lab calorimetric system after the leaving for 168 hours,respectively.)

(B) The content of a water-soluble organic solvent in which theevaporation rate X (mass %) and the moisture absorptivity Y (mass %)satisfy a relationship represented by the following expression (2) inall the water-soluble organic solvents in the ink is 50 mass % or more.Y≦2.8X+10  (2)(In the expression (2), X represents an evaporation rate and Yrepresents a moisture absorptivity.)

According to another aspect of the present invention, there is providedan ink jet recording method, comprising ejecting an ink by ink jetmethod, characterized in that the ink is the above-described ink jetink.

According to another aspect of the present invention, there is providedan ink cartridge including an ink storage portion for storing an ink,characterized in that the ink is the above-described ink jet ink.

According to another aspect of the present invention, there is provideda recording unit including an ink storage portion for storing an ink anda recording head for ejecting the ink, characterized in that the ink isthe above-described ink jet ink.

According to another aspect of the present invention, there is providedan ink jet recording apparatus including an ink storage portion forstoring an ink and a recording head for ejecting the ink, characterizedin that the ink is the above-described ink jet ink.

According to the present invention, there can be provided: an ink jetyellow ink which satisfies color developability requested for ink jetink and has high humidity resistance even when letters are printed bymeans of the ink on various recording media; and an ink jet recordingmethod, a recording unit, an ink cartridge, and an ink jet recordingapparatus each using the ink.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a relationship between an evaporation rate anda moisture absorptivity in the present invention.

FIG. 2 is a perspective view of a recording apparatus.

FIG. 3 is a perspective view of a mechanism, portion of the recordingapparatus.

FIG. 4 is a sectional view of the recording apparatus.

FIG. 5 is a perspective view showing a state where an ink tank ismounted on a head cartridge.

FIG. 6 is an exploded perspective view of the head cartridge.

FIG. 7 is a front view showing a recording element substrate in the headcartridge.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in more detail byway of preferred embodiments.

In the present invention, when a compound is a salt, the salt isdissociated to ions in ink, but this state is represented by using thephrase “contains a salt” for convenience.

<Ink>

The inventors of the present invention have revealed that migrationresults from an interaction between the humidity resistance of acoloring material and a water-soluble organic solvent. Hereinafter, acomponent constituting the ink according to the present invention andthe like will be described in detail.

(Coloring Material)

The ink jet ink according to the present invention (which mayhereinafter be simply referred to as the “ink”) must contain a coloringmaterial having a color difference (ΔE) judged by means of a method ofjudging properties of a coloring material to be described later of 9 orless.

[Method of Judging Properties of Coloring Material]

The method of judging properties of a coloring material in the presentinvention includes the above-described steps (1) to (3). Those stepswill be described in more detail by dividing them into the followingsteps (a) to (g).

(a) Preparation of Model Ink and Clear Ink

Prepared are a model ink containing a coloring material, water, and awater-soluble organic solvent having an evaporation rate X (mass %)smaller than that of water and a moisture absorptivity Y (mass %) whichis 20 mass % or more and satisfies a relationship of Y≧2.8X+10, orpreferably Y>2.8X+10 (the technical meaning of Y≧2.8X+10 will bedescribed later), and a clear ink prepared by replacing the coloringmaterial in the above composition with water. With the composition, theink has a condition under which migration tends to occur. It isimportant for the composition to satisfy the above condition because thecomposition aims at judging the properties (especially humidityresistance) of a coloring material.

The evaporation rate X (mass %) in the present invention is determinedby: placing 5 g of a water-soluble organic solvent into a dish having anouter diameter of 31 mm and a height of 15 mm; leaving the dish to standstill in an environment having a temperature of 60° C. and a humidity of10% for 192 hours; measuring the mass of the water-soluble organicsolvent again; and determining the evaporation rate from the reducedmass of the water-soluble organic solvent. The moisture absorptivity Y(mass %) is determined by: placing 5 g of a water-soluble organicsolvent into a dish having an outer diameter of 31 mm and a height of 15mm; leaving the dish to stand still in an environment having atemperature of 30° C. and a humidity of 80% for 192 hours; measuring themass of the water-soluble organic solvent again; and determining themoisture absorptivity from the increased mass of the water-solubleorganic solvent.

A specific example of the composition of a model ink includes thefollowing composition. A model ink was prepared according to thefollowing composition by using glycerin and urea as water-solubleorganic solvents, Acetylenol E-100 (manufactured by Kawaken FineChemicals Co., Ltd.) as a surfactant, and C.I. Direct Yellow 132 as acoloring material. Table 1 shows the evaporation rate X (mass %) andmoisture absorptivity (mass %) of each of glycerin and urea, and theevaporation rate X (mass %) of water (pure water). Table 1 below showsthat each of glycerin and urea corresponds to a water-soluble organicsolvent having an evaporation rate smaller than that of water and amoisture absorptivity of 20 mass % or more. TABLE 1 Evaporation MoistureComposition rate absorptivity [mass %] [mass %] [mass %] Glycerin 10.00.0 66.9 Urea 10.0 0.1 86.0 Acetylenol 1.0 — — E-100 C.I. Direct 3.0 — —Yellow 132 Pure water 76.0 100.0 —

(b) Creation of Image for Evaluation

The model ink and the clear ink thus prepared are superimposed to createan image for evaluation. Although the image may have an arbitraryprinting duty, it is important to superimpose the model ink and theclear ink. This is because, in general, printing is seldom performed bymeans of one kind of ink alone in consideration of the state of arecorded article in an actual environment. In other words, it can besaid that migration occurs in a situation where multiple inks arepresent. Therefore, it is important to create an image for evaluation bysuperimposing a model ink and a clear ink in order to reproduce thesituation. Furthermore, the amount of the model ink to be applied ispreferably smaller than that of the clear ink. This is because, when animage for evaluation is created by superimposing a model ink and a clearink under the above-described condition, the amount of a water-solubleorganic solvent to be applied with respect to a coloring materialincreases on a recording medium, with the result that migration is morelikely to occur. This approach enables a difference in property(especially humidity resistance) between coloring materials to berepresented with improved clarity, so the properties (especiallyhumidity resistance) of a target coloring material can be judged withimproved clarity. In the present invention, the above model ink and theabove clear ink were used, and each of them was changed in the dutyrange of 5 to 100% in an increment of 5% to create an image forevaluation in which the model ink and the clear ink were superimposed.

In the present invention, the evaluation of a coloring material forproperties (especially humidity resistance) does not require a specificrecording apparatus or recording medium. The shapes of a recordingapparatus and a recording medium are not limited as long as therecording apparatus applies ink to the recording medium and therecording medium can receive the ink. A specific example of suchrecording apparatus includes a recording apparatus including: an inkstorage portion for storing ink; and a recording head for ejecting theink.

(c) Creation of Image for Evaluation in Initial Standard State

The evaporation of each of the water-soluble organic solvent and waterpresent in the image for evaluation thus created is promoted. The imagefor evaluation is left in an environment having a temperature of T₁° C.and a humidity of H₁% for a certain period of time to promote theevaporation of each of the water-soluble organic solvent and waterpresent in the image for evaluation. As a result, an image forevaluation in an initial standard state can be created. It is importantto reduce the absolute water content of the environment in which theimage for evaluation is placed in order to promote the evaporation ofeach of the water-soluble organic solvent and water in the image forevaluation.

Although it is important to leave the image for evaluation in an initialstandard state in the environment having a temperature of T₁° C. and ahumidity of H₁% for a certain period of time, the period may bearbitrary. To be specific, the period is preferably such that theevaporation of each of the water-soluble organic solvent and water frominside the image for evaluation is reduced and the mass of the image forevaluation becomes constant. For example, the inventors have confirmedthat the evaporation of each of the water-soluble organic solvent andwater from inside the image for evaluation reaches substantialequilibrium in 48 hours and the mass of the image for evaluation becomesconstant in an environment having a temperature of T₁=25° C. and ahumidity of H₁=60%, the temperature and the humidity being selected byassuming the state of a recorded article in an actual environment.

When the image for evaluation is left for shorter than 48 hours, theevaporation of each of the water-soluble organic solvent and water doesnot reach equilibrium, and hence the water-soluble organic solvent orwater is expected to remain in the image for evaluation. As a result,the initial standard state is not stabilized, and there is a possibilitythat the state of occurrence of migration changes and the accuracy ofjudgment of humidity resistance reduces. When the image for evaluationis left for longer than 48 hours, the initial standard state can bestabilized, but the evaporation of each of the water-soluble organicsolvent and water from inside the image for evaluation is expected to beadditionally promoted. As a result, the amount of a water-solubleorganic solvent remaining in the image for evaluation, the water-solubleorganic solvent being expected to result in migration, reduces and theamount of a water-soluble organic solvent capable of absorbing moisturereduces. Accordingly, there is a possibility that migration hardly tendsto occur. In view of the foregoing reasons, the image for evaluation ispreferably left in the environment having a temperature of T₁=25° C. anda humidity of H₁=60% for 48 hours. Under the above condition, theevaporation of each of the water-soluble organic solvent and water inkeeping with the state of a recorded article in an actual environment isexpected to be realized. It should be noted that the absolute watercontent present in the environment having a temperature of 25° C. and ahumidity of 60% is about 13.8 g/m³.

(d) Measurement of Color Tone of Image for Evaluation in InitialStandard State

The color tone (CIE-La*b* values) of the image for evaluation in theinitial standard state thus created is measured. This measurementintends to numerically grasp the color tone of the image for evaluationin the initial standard state left for a certain period of time. In thepresent invention, the color tone of the image for evaluation in theinitial standard state was measured by means of a spectrophotometer(trade name: Spectrolino; manufactured by Gretag Macbeth).

(e) Creation of Image for Evaluation after Acceleration Test

The image for evaluation in the initial standard state thus created isleft in a (high-temperature-and-high-humidity) environment having atemperature of T₂° C. and a humidity of H₂% to cause migration to occurat an increasingly fast rate, thereby creating an image for evaluationafter an acceleration test. The temperature and the humidity at the timeof acceleration are arbitrary, provided that T₁<T₂ and H₁<H₂. That is,it is important to increase the absolute water content present in theenvironment by setting a higher temperature and a higher humidity. Ingeneral, migration is considered to occur when a water-soluble organicsolvent present in a recorded article absorbs moisture. Accordingly, itis important to promote the occurrence of migration by increasing theabsolute water content present in the environment in which the image forevaluation is placed. To be specific, the temperature T₂° C. ispreferably 30° C. or higher and the humidity H₂% is preferably 80% orhigher because the absolute water content present in the environment inwhich the image for evaluation is placed can be increased. In thepresent invention, in view of the conditions of a recording apparatusand a recorded article in an actual environment, the temperature T₂° C.and the humidity H₂% are set to 30° C. and 80%, respectively. As aresult, a condition under which migration may occur in a recordedarticle when an actual user uses a recording apparatus is reproduced. Itshould be noted that the absolute water content present in theenvironment having a temperature of 30° C. and a humidity of 80% isabout 24.3 g/m³.

The time period during which the image for evaluation is left in the(high-temperature-and-high-humidity) environment having a temperature ofT₂° C. and a humidity of H₂% is set by chronologically following achange in color tone of the image for evaluation. To be specific, achange in color tone of the image for evaluation from the initialstandard state is recorded, and the point at which a rate of changereduces is preferably set to be the time period during which the imagefor evaluation in the initial standard state is left in the(high-temperature-and-high-humidity) environment having a temperature ofT₂° C. and a humidity of H₂%. More preferably, the point at which nearlyno change in color tone is observed is set to be an appropriate timeperiod during which the image for evaluation in the initial standardstate is left in the (high-temperature-and-high-humidity) environmenthaving a temperature of T₂° C. and a humidity of H₂%. For example, arate of change in color tone will reduce in an environment having atemperature of T₂=30° C. and a humidity of H₂=80% in 96 hours, andnearly no change in color tone will be observed in the environment in168 hours. Therefore, it is important to leave the image for evaluationin the initial standard state in the(high-temperature-and-high-humidity) environment having a temperature ofT₂° C. and a humidity of H₂% for 96 hours or longer in order to evaluatemigration. More preferably, the image for evaluation in the initialstandard state is left in the (high-temperature-and-high-humidity)environment having a temperature of T₂° C. and a humidity of H₂% for 168hours or longer because a change in color tone shows a nearly constantvalue, so a difference in property (especially humidity resistance)between coloring materials can be judged with improved accuracy. In viewof the foregoing reasons, the image for evaluation is preferably left inthe environment having a temperature of T₂=30° C. and a humidity ofH₂=80% for 168 hours.

(f) Measurement of Color Tone of Image for Evaluation after AccelerationTest

The color tone (CIE-La*b* values) of the image for evaluation after theacceleration test thus created is measured. This measurement intends tonumerically grasp the color tone of the image for evaluation after theacceleration test. To be specific, the color tone of the image forevaluation after the acceleration test was measured by means of aspectrophotometer (trade name: Spectrolino; manufactured by GretagMacbeth) in the same manner as that of the above (d).

(g) Calculation of Color Difference (ΔE)

The color difference (ΔE) was calculated on the basis of the followingexpression (1) from the color tone (CIE-La*b* values) of the image forevaluation in the initial standard state measured in the above (d) andthe color tone (CIE-La*b* values) of the image for evaluation after theacceleration test measured in the above (f).

Values of La*b* in a CIE-La*b* color space of the image for evaluationin the initial standard state=(L₁, a₁, b₁)

Values of La*b* in the CIE-La*b* color space of the image for evaluationafter the acceleration test=(L₂, a₂, b₂)ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}  (1)

The color difference (ΔE) calculated on the basis of the expression (1)represents an amount of change in color tone. Therefore, the larger thecolor difference (ΔE), the larger the change in color tone. In otherwords, a larger color difference (ΔE) means that migration tends tooccur, so the degree of migration can be numerically represented bymeans of the color difference (ΔE).

In the present invention, the following procedure is essential. Eachcoloring material is evaluated for properties (especially humidityresistance) by means of the above-described method of judging propertiesof a coloring material, the color differences (ΔE) ΔE1, ΔE2, . . . inthe respective images for evaluation created by means of the respectivecoloring materials are calculated, and a coloring material having themaximum color difference (ΔE) out of the calculated color differences of9 or less is used.

(Coloring Material Represented by General Formula (I))

Another embodiment of the present invention is characterized in that thecoloring material having a color difference (ΔE) judged by means of themethod of judging properties of a coloring material of 9 or less is acompound represented by the following general formula (I) or a saltthereof.

(In the general formula (I), M's each independently represent a hydrogenatom, an alkali metal, an alkali earth metal, a cation of organic amineor an ammonium ion, and n's each independently represent 1 or 2.)

Specific examples of the coloring material represented by the generalformula (I) include compounds having structures shown in Table 2 below.Of course, the present invention is not limited to them. In Table 1, forconvenience, the substitution position of a sulfone group is representedby means of an A ring or a B ring as shown in the following generalformula (II). The substitution position of a sulfone group is as definedin the following general formula (II).

(In the general formula (II), M's each independently represent ahydrogen atom, an alkali metal, an alkali earth metal, a cation oforganic amine or an ammonium ion, and n's each independently represent 1or 2.) TABLE 2 Position of substituent A ring B ring Exemplified 1 2 4Compound 2 4 4 3 2 4, 6 4 4, 6 4

A preferable specific example of the coloring material represented bythe general formula (I) includes Exemplified Compound 1 below. Ofcourse, the present invention is not limited to it.

[Coloring Material except Coloring Material Represented by GeneralFormula (I)]

In the present invention, two or more kinds of coloring materials arepreferably used for additionally increasing an image density, forobtaining a more preferable color tone, and for other purposes. Thecoloring material represented by the general formula (I) and C.I. DirectYellow 132 are particularly preferable as such coloring materials.Accordingly, another embodiment of the present invention ischaracterized in that C.I. Direct Yellow 132 is incorporated as acoloring material in addition to the coloring material represented bythe general formula (I).

[Content of Coloring Material]

The content of a coloring material in the ink jet ink according to thepresent invention is preferably 1.0 mass % or more and 4.0 mass % orless with respect to the total mass of the ink. When the content of acoloring material is smaller than 1.0 mass %, effects of the presentinvention such as color developability and humidity resistance cannot besufficiently obtained in some cases. When the content of a coloringmaterial exceeds 4.0 mass %, reliability such as start up ejectionstability and other ink jet properties may reduce.

In addition, the content of the coloring material represented by thegeneral formula (I) is preferably 10 mass % or more with respect to thetotal content of all the coloring materials in the ink in order tosufficiently obtain the effects of the present invention. When C.I.Direct Yellow 132 is used in combination, its content is preferably 10mass % or more with respect to the total content of the coloringmaterials in the ink. Furthermore, a ratio of the content of thecoloring material represented by the general formula (I) to the contentof C.I. Direct Yellow 132 (the content of the coloring materialrepresented by the general formula (I): the content of C.I. DirectYellow 132) is in the range of 0.5:5 to 2:5 in mass ratio. Anexcessively small content of the coloring material represented by thegeneral formula (I) makes it difficult to obtain a significant effect ofthe present invention, while an excessively large content of thecoloring material tends to reduce an image density.

[Method of Testing Coloring Material]

Exemplified Compound 1, which is an example of the coloring material tobe used in the present invention, can be tested by the following methods(1) to (3) each of which involves the use of high performance liquidchromatography (HPLC).

(1) Retention time of the peak

(2) Maximum absorption wavelength in the peak of (1)

(3) M/Z (posi, nega) of mass spectrum in the peak of (1)

Analysis conditions for high performance liquid chromatography are asshown below. An ink solution diluted 1,000 times with pure water isanalyzed by means of high performance liquid chromatography under thefollowing conditions to measure the retention time of a main peak andthe maximum absorption wavelength of a peak.

Column: Symmetry C18 2.1 mm×150 mm

Column temperature: 40° C.

Flow rate: 0.2.ml/min

PDA: 210 nm to 700 nm

Mobile phase and gradient condition: Table 3 TABLE 3 0-5 min 5-40 min40-45 min A Water 85% 85%→0%  0% B Methanol 10% 10%→95% 95% C 0.2-mol/laqueous 5% 5% 5% solution of ammonium acetate

In addition, analysis conditions for a mass spectrum are as shown below.The mass spectrum of the resultant peak is measured under the followingconditions, and the most strongly detected M/Z is measured for each ofposi and nega. Ionization method ESI Capillary voltage 3.5 kVDesolvating gas 300° C. Ion source temperature 120° C. Detector posi 40V 200-1,500 amu/0.9 sec nega 40 V 200-1,500 amu/0.9 sec

Table 4 shows the values of the retention time, maximum absorptionwavelength, M/Z (posi), and M/Z (nega) of each of Exemplified Compound 1and C.I. Direct Yellow 132. When a coloring material has a value shownin Table 4, the coloring material can be judged to be a coloringmaterial used in the present invention. TABLE 4 Maximum Retentionabsorption time wavelength M/Z [min ] [nm] Posi Nega Exemplified 31-32390-410 938-939 468-469 Compound 1 C.I. Direct 33-34 390-410 640-641319-320 Yellow 132

(Water-Soluble Organic Solvent)

Water-soluble organic solvents to be used in the ink of the presentinvention must be such that the content of a water-soluble organicsolvent in which the evaporation rate X (mass %) and the moistureabsorptivity Y (mass %) satisfy the relationship represented by thefollowing expression (2) with respect to the total content of thewater-soluble organic solvents in the ink is 50 mass % or more.

Migration is considered to occur when a water-soluble organic solventpresent in a recorded article absorbs moisture. Therefore, migration canbe suppressed by incorporating a certain amount or more of awater-soluble organic solvent which readily evaporates and has a lowmoisture absorptivity into ink. However, ink containing only awater-soluble organic solvent which readily evaporates and has a lowmoisture absorptivity tends to be problematic in terms of adhesion atthe tip of a nozzle, start up ejection stability, and the like. In thepresent invention, ink with suppressed migration, suppressed adhesion atthe tip of a nozzle, and, for example, excellent start up ejectionstability can be obtained when a water-soluble organic solvent satisfiesthe above constitution.Y≦2.8X+10  (2)(In the expression (2), X represents an evaporation rate and Yrepresents a moisture absorptivity.)

The evaporation rate X (mass %) in the present invention is determinedby: placing 5 g of a water-soluble organic solvent into a dish having anouter diameter of 31 mm and a height of 15 mm; leaving the dish to standstill in an environment having a temperature of 60° C. and a humidity of10% for 192 hours; measuring the mass of the water-soluble organicsolvent again; and determining the evaporation rate from the reducedmass of the water-soluble organic solvent. The moisture absorptivity Y(mass %) is determined by: placing 5 g of a water-soluble organicsolvent into a dish having an outer diameter of 31 mm and a height of 15mm; leaving the dish to stand still in an environment having atemperature of 30° C. and a humidity of 80% for 192 hours; measuring themass of the water-soluble organic solvent again; and determining themoisture absorptivity from the increased mass of the water-solubleorganic solvent. FIG. 1 is a graph showing a relationship between theevaporation rate and moisture absorptivity of each water-soluble organicsolvent calculated by means of the above method. In the figure, Gly,DEG, PEG, 2P, 15PD, 16HD, 126HT, Urea, and EtUrea represent glycerin,diethylene glycol, polyethylene glycol, 2-pyrrolidone, 1,5-pentanediol,1,6-hexanediol, 1,2,6-hexanetriol, urea, and ethylene urea,respectively.

Ink containing each of the above respective water-soluble organicsolvents was prepared, and the following experiment was performed. Amodel ink was prepared, which contained 3 mass % of C.I. Direct Yellow132, 20 mass % of each water-soluble organic solvent, and 0.5 mass % ofAcetylenol E-100 (manufactured by Kawaken Fine Chemicals Co., Ltd.) as asurfactant, the balance being water. Separately from the model ink, aclear ink was prepared by replacing the coloring material with water.Each of the resultant model ink and the resultant clear ink was changedin the duty range of 0 to 100% to create a recorded article havingformed thereon an image in which the model ink and the clear ink weresuperimposed. A PIXUS 950i (manufactured by CANON Inc.) as an ink jetprinter and a super photo paper (SP-101; manufactured by CANON Inc.) asa recording medium were used for creating the recorded article.

The resultant recorded article was left in a(normal-temperature-and-normal-humidity) environment having atemperature of 25° C. and a humidity of 60% for 48 hours to cause thewater-soluble organic solvent and water to evaporate from the recordingmedium. The color tone (CIE-La*b* values) after the leaving in theenvironment having a temperature of 25° C. and a humidity of 60% for 48hours was measured by means of a spectrophotometer (trade name:Spectrorino; manufactured by Gretag Macbeth) to determine the values ofLa*b*. After that, the resultant recorded article was left in a(high-temperature-and-high-humidity) environment having a temperature of30° C. and a humidity of 80% for 168 hours to cause the water-solubleorganic solvent to migrate. The color tone (CIE-La*b* values) after theleaving in the environment having a temperature of 30° C. and a humidityof 80% for 168 hours was measured by means of the same spectrophotometeras that described above to determine the values of La*b* after themigration of the water-soluble organic solvent. The maximum colordifference (ΔE) was determined from the obtained results. It can be saidthat the larger the color difference (ΔE), the larger a change in colortone in a high-temperature-and-high-humidity environment and the lowerthe humidity resistance.

The above experimental results, and the relationship between theevaporation rate and moisture absorptivity of each water-soluble organicsolvent showed that there is a correlation between the evaporation rateand the moisture absorptivity.

Migration refers to image deterioration due to a change in color tonein, for example, a high-temperature-and-high-humidity environment.Therefore, the lower the color difference caused by an environment, thebetter the migration property of the water-soluble organic solvent. Awater-soluble organic solvent having good migration property, that is,good humidity resistance has a characteristic in that the solventreadily evaporates and hardly absorbs moisture. In other words, awater-soluble organic solvent having better migration property shows asmaller color difference (ΔE).ΔE≦5.5ΔE>5.5

In general, an image having a color difference (ΔE) of 5.5 or less ispreferable because no change in color tone due to migration occurs evenin a high-temperature-and-high-humidity environment. In contrast, animage having a color difference (ΔE) of larger than 5.5 shows aremarkable change in color tone due to migration in ahigh-temperature-and-high-humidity environment, to thereby deteriorate.The expression (2) is obtained by finding the relationship among themigration of each water-soluble organic solvent, and the evaporationrate and moisture absorptivity of the solvent on the basis of the abovecriterion. That is, in FIG. 1, a water-soluble organic solvent on theright side with respect to the line of Y=2.8X+10 has a color difference(ΔE) of 5.5 or less.

In general, a water-soluble organic solvent (poor solvent) having lowsolubility for a coloring material can also be used for improvinghumidity resistance. However, none of the coloring materials to be usedin the present invention showed a relationship between migration and thesolubility of the coloring material in a water-soluble organic solvent.That is, not the solubility of a coloring material to be used in thepresent invention in a water-soluble organic solvent but the evaporationrate and moisture absorptivity of a water-soluble organic solvent in inkhold a dominant position in the improvement of the humidity resistanceof the coloring material to be used in the present invention.

Specific examples of the water-soluble organic solvent satisfying therelationship represented by the expression (2) include ethylene glycol,diethylene glycol, 2-pyrrolidone, 1,5-pentanediol, 1,6-hexanediol,ethylene urea, N-methyl-2-pyrrolidone, butyl carbitol, and isopropylalcohol. Of those, ethylene glycol, diethylene glycol, 2-pyrrolidone,1,5-pentanediol, 1,6-hexanediol, and ethylene urea are preferable, andethylene urea is particularly preferable. Ethylene urea, diethyleneglycol, and 2-pyrrolidone are particularly preferably used incombination for improving ink jet properties such as reliability. Anywater-soluble organic solvent other than those described above may beused as long as the solvent satisfies the relationship represented bythe expression (2).

In the ink according to the present invention, a water-soluble organicsolvent that does not satisfy the relationship represented by theexpression (2) such as glycerin, urea, or polyethylene glycol can beused to the extent that the addition of such water-soluble organicsolvent has an effect, and the objects and effects of the presentinvention are not impaired. However, the content of a water-solubleorganic solvent satisfying the relationship represented by theexpression (2) with respect to the total content of the water-solubleorganic solvents in the ink must be 50 mass % or more in order tosufficiently obtain the effects of the present invention. The content ofa water-soluble organic solvent satisfying the relationship representedby the expression (2) with respect to the total content of thewater-soluble organic solvents in the ink is preferably 65 mass % ormore because the effects of the present invention are efficientlyexerted.

In the present invention, the content of a water-soluble organic solventsatisfying the relationship represented by the expression (2) withrespect to the total mass of all the water-soluble organic solvents inthe ink is 50 mass % or more. When the content of a water-solubleorganic solvent satisfying the relationship represented by theexpression (2) is excessively small, a significant effect of the presentinvention cannot be obtained.

Meanwhile, the total content of all the water-soluble organic solventsin the ink is preferably 10 mass % or more and 50 mass % or less withrespect to the total mass of the ink. When the total content of thewater-soluble organic solvents is smaller than 10 mass % or exceeds 50mass %, ink jet properties such as reliability may deteriorate.

(Other Additive)

The ink of the present invention may use moisture-retaining solidcontents such as urea and a urea derivative as ink components asrequired.

In addition, the ink of the present invention may be added with variousadditives such as a surfactant, a pH adjustor, a rust inhibitor, anantiseptic, an antifungus agent, an antioxidant, a reduction inhibitor,an evaporation accelerator, a chelating agent, and a water-solublepolymer.

<Recording Medium>

Any recording medium can be used for forming an image by means of theink of the present invention as long as recording is performed byapplying the ink to the recording medium.

The present invention is applicable to a recording medium in which acoloring material such as a pigment is adsorbed to a fine particleforming a porous structure in an ink-receiving layer and an image isformed from at least the fine particle having adsorbed thereto thecoloring material, and the present invention is particularly suitablefor the case where an ink jet method is used. Such ink jet recordingmedium is preferably of a so-called absorption type in which ink isabsorbed by a gap formed in an ink-receiving layer on a support.

An absorption type ink-receiving layer is constituted as a porous layermainly composed of a fine particle and containing a binder and any otheradditive as required. Specific examples of the fine particle include:inorganic pigments such as silica, clay, talc, calcium carbonate,kaolin, aluminum oxide (for example, alumina or alumina hydrate),diatomaceous earth, titanium oxide, hydrotalcite, and zinc oxide; andorganic pigments such as a urea formalin resin, an ethylene resin, and astyrene resin. One or more kinds of them are used. Examples of a binderthat is suitably used include a water-soluble polymer and a latex.Examples of an available binder include: polyvinyl alcohol or adenatured product thereof; starch or a denatured product thereof;gelatin or a denatured product thereof; gum arabic; cellulosederivatives such as carboxymethylcellulose, hydroxyethylcellulose, andhydroxyproylmethylcellulose; vinyl-based copolymer latexes such as anSBR latex, an NBR latex, a methyl methacrylate-butadiene copolymerlatex, a functional group-denatured polymer latex, and an ethylene-vinylacetate copolymer; polyvinyl pyrrolidone; maleic anhydride or acopolymer thereof; and an acrylate copolymer. Two or more kinds of themcan be used in combination as required. In addition, an additive may beused, and examples of an additive to be used as required include adispersant, a thickener, a pH adjustor, a lubricant, a fluiditydenaturing agent, a surfactant, a defoaming agent, a releasing agent, afluorescent bleach, a UV absorber, and an antioxidant.

In particular, a recording medium having formed thereon an ink-receivinglayer mainly composed of fine particles having an average particle sizeof 1 μm or less is preferably used in the present invention.Particularly preferable examples of the fine particles include silicafine particles and aluminum oxide fine particles. Preferable silica fineparticles are silica fine particles typified by colloidal silica.Colloidal silica, which itself is available from the market, isparticularly preferably that described in JP 2803134 B or JP 2881847 B.Preferable aluminum oxide fine particles are alumina hydrate fineparticles and the like. An alumina hydrate represented by the followinggeneral formula can be exemplified as one example of such aluminahydrate fine particles.AlO _(3-n)(OH)_(2n)·mH₂O(In the formula, n represents an integer of 1, 2, or 3, and m representsa value of 0 to 10, or preferably 0 to 5; provided, however, that m andn cannot be simultaneously 0. m may be or may not be an integer becausemH₂O also represents an aqueous phase that can desorb and is notinvolved in the formation of an mH₂O crystal lattice in many cases. Inaddition, heating such kind of material may cause m to reach 0.)

An alumina hydrate can be produced by means of a conventionally knownmethod such as: the hydrolysis of aluminum alkoxide or sodium aluminatedescribed in U.S. Pat. No. 4,242,271 or U.S. Pat. No. 4,202,870; or amethod involving adding an aqueous solution of sodium sulfate, aluminumchloride, or the like to an aqueous solution of sodium aluminate or thelike to perform neutralization described in JP-B57-44605.

The recording medium preferably has a support for supporting theabove-described ink-receiving layer. Any support can be use without anyparticular limitation as long as its ink-receiving layer can be formedof the above-described porous fine particles and the support providesrigidity such that the ink-receiving layer can be conveyed by aconveying mechanism of an ink jet printer or the like. Specific examplesthereof include: a paper support formed of a pulp raw material mainlycomposed of natural cellulose fibers; a plastic support composed of amaterial such as polyester (for example, polyethylene terephthalate),cellulose triacetate, polycarbonate, polyvinyl chloride, polypropylene,or polyimide; resin-coated paper (for example, RC paper) having, on atleast one side of base paper, a polyolefin resin coating layer addedwith a white pigment or the like.

<Ink Set>

The ink of the present invention can also be preferably used even whenthe ink is combined with any other ink to provide an ink set. The inkset in the present invention refers to a state where the ink of thepresent invention is used in combination with another ink such as cyanink, magenta ink, yellow ink, or black ink. The other ink that can becombined to provide an ink set is not limited. The ink set in thepresent invention also includes the case where multiple ink tanks arecombined and used as well as an ink tank itself having multiple inktanks integrated with each other. The ink set further includes anintegrated product of the ink tank and a recording head.

<Ink Jet Recording Method>

The ink according to the present invention is particularly suitably usedfor an ink jet recording method including the step of ejecting the inkby means of an ink jet method. Examples of the ink jet recording methodinclude a recording method involving applying mechanical energy to inkto eject the ink and a recording method involving applying thermalenergy to ink to eject the ink. An ink jet recording method involvingthe use of thermal energy is particularly preferably used in the presentinvention.

<Ink Cartridge>

An example of an ink cartridge suitable for performing recording bymeans of the ink according to the present invention includes an inkcartridge including an ink storage portion for storing the ink.

<Recording Unit>

An example of a recording unit suitable for performing recording bymeans of the ink according to the present invention includes a recordingunit including an ink storage portion for storing the ink and arecording head. In particular, a recording unit in which the recordinghead applies thermal energy corresponding to a recording signal to theink to generate an ink droplet by virtue of the energy can beexemplified.

<Ink Jet Recording Apparatus>

An example of a recording apparatus suitable for performing recording bymeans of the ink according to the present invention includes a recordingapparatus in which thermal energy corresponding to a recording signal isapplied to ink in the chamber of a recording head having an ink storageportion for storing the ink to generate an ink droplet by virtue of theenergy.

Hereinafter, the schematic constitution of a mechanism portion of an inkjet recording apparatus will be described. A recording apparatus mainbody is constituted by a sheet feeding portion, a sheet conveyingportion, a carriage portion, a sheet discharge portion, and a cleaningportion, and an external packaging portion for protecting them andproviding them with design to achieve a role of each mechanism.Hereinafter, the outline of each of them will be described.

FIG. 2 is a perspective view of a recording apparatus. FIGS. 3 and 4 areviews for explaining the internal mechanism of a recording apparatusmain body. FIG. 3 is a perspective view seen from an upper rightportion, and FIG. 4 is a side sectional view of the recording apparatusmain body.

When a sheet is to be fed in the recording apparatus, only apredetermined number of recording media are sent to a nip portioncomposed of a sheet feeding roller M2080 and a separating roller M2041in the sheet feeding portion including a sheet feeding tray M2060. Thesent recording media are separated at the nip portion, and only theuppermost recording medium is conveyed. The recording medium sent to thesheet conveying portion is guided by a pinch roller holder M3000 and apaper guide flapper M3030 to be sent to a roller pair composed of aconveying roller M3060 and a pinch roller M3070. The roller paircomposed of the conveying roller M3060 and the pinch roller M3070 arerotated by the driving of an LF motor E0002, and the rotation causes therecording medium to be conveyed on a platen M3040.

In the carriage portion, when an image is to be formed on a recordingmedium, a recording head H1001 (FIG. 5) is arranged at a target imageforming position, and ink is ejected to the recording medium inaccordance with a signal from an electrical substrate E0014. Detailsabout the constitution of the recording head H1001 will be describedlater. While recording is performed by the recording head H1001,recording main scanning in which a carriage M4000 scans in a columndirection and sub scanning in which a recording medium is conveyed in arow direction by the conveying roller M3060 are alternately repeated,whereby an image is formed on the recording medium.

Finally, the recording medium on which an image has been formed issandwiched at a nip between a first sheet discharge roller M3110 and aspur M3120 in the sheet discharge portion, conveyed, and discharged to asheet discharge tray M3160.

In the cleaning portion, when a pump M5000 is allowed to act in a statewhere a cap M5010 is brought into close contact with an ink ejectionport of the recording head H1001 for the purpose of cleaning therecording head H1001 before and after image recording, unnecessary inkand the like are sucked from the recording head H1001. The ink remainingin the cap M5010 is sucked with the cap M5010 opened, whereby neitheradhesion of the remaining ink nor a subsequent harmful effect occurs.

(Constitution of Recording Head)

The constitution of a head cartridge H1000 will be described. The headcartridge H1000 includes the recording head H1001, means for mountingink tanks H1900, and means for supplying ink from the ink tanks H1900 tothe recording head, and is detachably mounted on the carriage M4000.

FIG. 5 shows how the ink tanks H1900 are mounted on the head cartridgeH1000. The recording apparatus forms an image by means of yellow,magenta, cyan, black, pale magenta, pale cyan, and green inks, so theink tanks H1900 are independently prepared for seven colors. The inkaccording to the present invention is used for at least one of the aboveinks. In addition, as shown in the figure, each ink tank is detachableto the head cartridge H1000. The ink tanks H1900 can be detached in astate where the head cartridge H1000 is mounted on the carriage M4000.

FIG. 6 shows an exploded perspective view of the head cartridge H1000.In the figure, the head cartridge H1000 includes a first recordingelement substrate H1100, a second recording element substrate H1101, afirst plate H1200, a second plate H1400, an electric wiring substrateH1300, a tank holder H1500, a flow path forming member H1600, a filterH1700, and a seal rubber H1800.

Each of the first recording element substrate H1100 and the secondrecording element substrate H1101 is an Si substrate having multiplerecording elements (nozzles) for ejecting ink formed on one surface bymeans of photolithography. Electric wiring made of Al or the like forsupplying power to each recording element is formed by means of a filmformation technique, and multiple ink flow paths corresponding to theindividual recording elements are also formed by means ofphotolithography. Furthermore, ink supply ports for supplying ink to themultiple ink flow paths are formed so as to open on the rear surface.

FIG. 7 is an enlarged front view for explaining the constitution of eachof the first recording element substrate H1100 and the second recordingelement substrate H1101. Reference symbols H2000 to H2600 denoterecording element trains (which may hereinafter be also referred to asnozzle trains) corresponding to different ink colors. The firstrecording element substrate H1100 has nozzle trains for three colors:the nozzle train H2000 to which yellow ink is supplied, the nozzle trainH2100 to which magenta ink is supplied, and the nozzle train H2200 towhich cyan ink is supplied. The second recording element substrate H1101has nozzle trains for four colors: the nozzle train H2300 to which palecyan ink is supplied, the nozzle train H2400 to which black ink issupplied, the nozzle train H2500 to which orange ink is supplied, andthe nozzle train H2600 to which pale magenta ink is supplied.

Each nozzle train is constituted by 768 nozzles arranged at an intervalof 1,200 dpi (dot/inch; reference value) in the conveying direction of arecording medium, and each nozzle ejects about 2 pl of ink. An openingarea in each nozzle ejection port is set to about 100 μm². The firstrecording element substrate H1100 and the second recording elementsubstrate H1101 are bonded and fixed to the first plate H1200 havingformed thereon ink supply ports H1201 for supplying ink to the firstrecording element substrate H1100 and the second recording elementsubstrate H1101.

The second plate H1400 having openings is also bonded and fixed to thefirst plate H1200. The second plate H1400 holds the electric wiringsubstrate H1300 in such a manner that the electric wiring substrateH1300, the first recording element substrate H1100, and the secondrecording element substrate H1101 are electrically connected.

The electric wiring substrate H1300 applies an electrical signal forcausing each of the nozzles formed on the first recording elementsubstrate H1100 and the second recording element substrate H1101 toeject ink. The electric wiring substrate H1300 has: electric wiringcorresponding to each of the first recording element substrate H1100 andthe second recording element substrate H1101; and an external signalinput terminal H1301 which is positioned at an end portion of theelectric wiring to receive an electrical signal from the recordingapparatus main body. The external signal input terminal H1301 ispositioned and fixed to the back surface side of the tank holder H1500.

Meanwhile, the flow path forming member H1600 is fixed by means of, forexample, ultrasonic welding to the tank holder H1500 for holding the inktanks H1900. Thus, an ink flow path H1501 passing from the ink tanksH1900 to the first plate H1200 is formed.

The filter H1700 is arranged at an end portion on the ink tank side ofthe ink flow path H1501 engaged with the ink tanks H1900, so the filterH1700 prevents dust from entering from the outside. The seal rubberH1800 is mounted on the portion at which the ink flow path H1501 isengaged with the ink tanks H1900 to prevent ink from evaporating fromthe portion.

Furthermore, as described above, the head cartridge H1000 is constitutedby connecting through bonding or the like a tank holder portionconstituted by: the tank holder H1500; the flow path forming memberH1600; the filter H1700; and the seal rubber H1800, and the recordinghead portion H1001 constituted by: the first recording element substrateH1100; the second recording element substrate H1101; the first plateH1200; the electric wiring substrate H1300; and the second plate H1400.

Description has been made here by taking, as an example of an embodimentof a recording head, a recording head according to a bubble jet(registered trademark) method that performs recording by means of anelectrothermal converter (recording element) that generates thermalenergy for causing ink to generate film boiling in accordance with anelectrical signal.

The representative structure and principle of a bubble jet method arepreferably based on basic principles disclosed in, for example, U.S.Pat. No. 4,723,129 and U.S. Pat. No. 4,740,796. The method is applicableto any one of so-called an on-demand type and a continuous type. Inparticular, the method is effective for the on-demand type because ofthe following reason. At least one driving signal which corresponds torecording information and causes a sudden increase in temperatureexceeding nuclear boiling is applied to an electrothermal converterarranged in correspondence with a sheet or liquid flow path holding aliquid (ink), to thereby cause the electrothermal converter to generatethermal energy. Then, a thermal action surface of a recording head iscaused to generate film boiling. As a result, an air bubble in theliquid (ink) can be formed so as to be in one-to-one correspondence withthe driving signal. The growth and contraction of the air bubble causethe liquid (ink) to be ejected through an opening for ejection, therebyforming at least one droplet. The driving signal is more preferably of apulse shape because the growth and contraction of an air bubble can beperformed immediately and appropriately, and hence the liquid (ink) canbe ejected with particularly excellent responsiveness.

An example of a second embodiment of an ink jet recording apparatusutilizing mechanical energy includes an on-demand ink jet recording headincluding: a nozzle forming substrate having multiple nozzles; pressuregenerating means arranged so as to be opposed to the nozzles andcomposed of a piezoelectric material and a conductive material; and inkfilling the surroundings of the pressure generating means, in which thepressure generating means is displaced through the application of avoltage to eject a small ink droplet from the nozzle.

The ink jet recording apparatus is not limited to such apparatus asdescribed above in which a head and an ink tank are separated, and maybe one in which a head and an ink tank are integrated so that they areunseparable. The ink tank may be separably or unseparably integratedwith the head to be mounted on a carriage, or may be mounted at a fixingportion of an apparatus to supply ink to a recording head through an inksupply member such as a tube. When the ink tank is provided with aconstitution for applying a preferable negative pressure to therecording head, an absorber may be arranged in an ink storage portion ofthe ink tank, or the ink tank may have a flexible ink storage bag and aspring portion for applying bias to expand the internal volume of thebag. The recording apparatus may adopt a serial recording method asdescribed above, or may be in the form of a line printer obtained byaligning recording elements over the range corresponding to the entirewidth of a recording medium.

EXAMPLES

Hereinafter, the present invention will be described by way of examplesand comparative examples. However, the present invention is not limitedto the following examples without departing from the gist of the presentinvention. Unless otherwise stated, the term “part” of each inkcomponent in examples and comparative examples represents “part bymass”.

<Preparation of Coloring Material>

Diazotized 4-nitro-4′-aminostilbene-2,2-disulfonic acid and3-aminonapthalene-1-sulfonic acid were subjected to coupling. Theresultant was turned into a triazole, and a nitro group of the triazolewas reduced to an amino group by means of a conventionally known methodto produce aminostilbene-triazole. Aminostilbene-triazole was dissolvedinto water, and sodium nitrite and hydrochloric acid were added dropwiseto the solution to perform diazotization. The resultant was addeddropwise to an aqueous solution of a compound represented by Compound(1) below, and the whole was subjected to coupling, followed by dialysiswith sodium chloride. The compound was diazotized with an aqueoussolution of sodium nitrite, and was turned into a triazole by adding anaqueous solution of 6-aminonaphthalene-2-sulfonic acid. The triazole wasdialyzed with sodium chloride to prepare a coloring material representedby Exemplified Compound 1 below.

<Judgment of Properties of Coloring Material>

Properties (humidity resistance) of Exemplified Compound 1 thus preparedand the respective coloring materials shown in Table 5 below were judgedby means of the method of judging properties of a coloring material ofthe present invention.

(Preparation of Model Ink and Clear Ink)

A model ink containing each coloring material was prepared according tothe following prescription. Each coloring material 3.0 parts Glycerin9.0 parts Urea 9.0 parts Acetylenol E100 1.0 part (manufactured byKawaken Fine Chemicals Co., Ltd.) Water Balance

Next, a clear ink was prepared by replacing the coloring material in theabove composition with water.

Water has an evaporation rate X (mass %) of 100 mass %. Glycerin andurea used as water-soluble organic solvents in the above compositionhave evaporation rates X (mass %) of 0 mass % and 0.1 mass %,respectively. In addition, glycerin has a moisture absorptivity Y (mass%) of 66.9 mass % and urea has a moisture absorptivity Y (mass %) of86.0 mass %. Therefore, each of glycerin and urea corresponds to awater-soluble organic solvent having an evaporation rate smaller thanthat of water and a moisture absorptivity of 20 mass % or more.

(Creation of Image for Evaluation and Calculation of Color Difference)

The model ink was changed in the duty range of 0% to 100% in anincrement of 5% and the clear ink was changed in the duty range of 0% to100% in an increment of 5% to create an image for evaluation having asuperimposed gradation pattern. An ink jet printer (trade name: PIXUS950i; manufactured by CANON Inc.) and a recording medium (trade name:SP-101; manufactured by CANON Inc.) were used for creating the image forevaluation. The resultant recorded article was left in an environmenthaving a temperature of 25° C. and a humidity of 60% for 48 hours, andthen the color tone of the superimposed gradation pattern portion wasmeasured by means of a spectrophotometer (trade name: Spectrorino;manufactured by Gretag Macbeth). The recorded article was additionallyleft in an environment having a temperature of 30° C. and a humidity of80% for 168 hours, and then the color tone was measured in the samemanner as that described above by means of the spectrophotometer as thatdescribed above. The color difference (ΔE) in the image for evaluationwas calculated on the basis of the following expression (1) from thecolor tone of the image for evaluation after having been left in theenvironment having a temperature of 25° C. and a humidity of 60% for 48hours and the color tone of the image for evaluation after having beenleft in the environment having a temperature of 30° C. and a humidity of80% for 168 hours.

Values of La*b* in a CIE-La*b* color space of the image for evaluationafter having been left in the environment having a temperature of 25° C.and a humidity of 60% for 48 hours (initial standard state)=(L₁, a₁, b₁)

Values of La*b* in the CIE-La*b* color space of the image for evaluationafter having been left in the environment having a temperature of 30° C.and a humidity of 80% for 168 hours (after an acceleration test)=(L₂,a₂, b₂)ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}  (1)

The maximum color difference (ΔE) out of the color differences in therespective images for evaluation calculated on the basis of theexpression (1) was calculated. Table 5 shows the results. TABLE 5Coloring material ΔE_(max) Exemplified Compound 1 7.5 C.I. Food Yellow 310.4

<Preparation of Ink>

Inks A to G of Examples and inks H to K of Comparative Examples wereprepared by means of Exemplified Compound 1 thus prepared and C.I. FoodYellow 3 according to the prescription shown in Table 6. TABLE 6 Ink A BC D E F G H I J K Exemplified Compound 1 3.0 4.5 3.0 3.0 3.0 3.0 3.0 3.03.0 3.0 C.I.Food Yellow 3 3.0 Ethylene glycol 4.0 11.2 Diethylene glycol9.2 9.2 9.2 5.2 5.0 9.2 9.2 9.2 10.0 2-pyrrolidone 5.0 5.0 5.0 2.0 5.09.4 6.0 5.0 5.0 Ethylene urea 5.0 5.0 2.0 2.0 5.0 1.5-pentanediol 5.0N-methyl-2-pyrrolidone 4.0 Butyl carbitol 2.0 Isopropyl alcohol 3.0 Urea9.0 5.0 10.0 Glycerin 9.0 7.0 9.0 8.0 8.0 10.0 10.0 8.0 5.0 9.0 5.5Polyethylene glycol (*1) 5.0 5.0 Acetylenol E100 (*2) 0.9 0.9 0.9 0.90.9 0.9 0.9 0.9 0.9 0.9 Surfynol 104PG50 (*3) 0.1 Ion-exchanged water67.9 68.4 67.9 69.9 69.9 76.1 67.5 58.9 77.9 67.9 60.6(*1) A molecular weight of 200(*2) Ethylene oxide adduct of acetylene glycol (surfactant)(manufactured by Kawaken Fine Chemicals Co., Ltd.)(*3) Surfactant; manufactured by Nissin Chemical Industry Co., Ltd.

<Printing Evaluation>

Clear inks A to K were prepared by replacing each of the coloringmaterials in the prescription of the inks A to G of Examples and theinks H to K of Comparative Examples thus obtained with pure water. Anink jet printer (trade name: PIXUS 950i; manufactured by CANON Inc.) wasused for the evaluation.

(1) Humidity Resistance of Ink

Each of the inks of Examples and Comparative Examples was changed in theduty range of 0% to 100% in an increment of 5% and the correspondingclear ink was changed in the duty range of 0% to 100% in an increment of5% to create an image for evaluation having a superimposed gradationpattern. The combination of the ink and the clear ink was thecombination of the ink A and the clear ink A, the combination of the inkB and the clear ink B, or the like. A glossy recording medium (SP-101;manufactured by CANON Inc.) was used as a recording medium. Theresultant recorded article was left in an environment having atemperature of 25° C. and a humidity of 60% for 48 hours, and then thecolor tone of the superimposed gradation pattern portion was measured bymeans of a spectrophotometer (trade name: Spectrorino; manufactured byGretag Macbeth). The recorded article was additionally left in anenvironment having a temperature of 30° C. and a humidity of 80% for 168hours, and then the color tone was measured in the same manner as thatdescribed above by means of the spectrophotometer as that describedabove. The color difference (ΔE) in each image for evaluation wascalculated on the basis of the following expression (1) from the colortone of the image for evaluation after having been left in theenvironment having a temperature of 25° C. and a humidity of 60% for 48hours and the color tone of the image for evaluation after having beenleft in the environment having a temperature of 30° C. and a humidity of80% for 168 hours.

Values of La*b* in the CIE-La*b* color space of the image for evaluationafter having been left in the environment having a temperature of 25° C.and a humidity of 60% for 48 hours (initial standard state)=(L₁, a₁, b₁)

Values of La*b* in the CIE-La*b* color space of the image for evaluationafter having been left in the environment having a temperature of 30° C.and a humidity of 80% for 168 hours (after an acceleration test)=(L₂,a₂, b₂)ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}  (1)

The maximum color difference (ΔE) out of the color differences in therespective images for evaluation calculated on the basis of theexpression (1) was calculated, and each ink was evaluated for humidityresistance on the basis of the following criteria. Table 7 shows theresults.

A 4.0≧ΔE

B 5.5≧ΔE>4.0

C 7.0≧ΔE>5.5

D ΔE>7.0

(2) Start up Ejection Stability

An ink jet printer on which an ink cartridge storing each of the inks ofExamples and Comparative Examples had been mounted was left in anenvironment having a temperature of 15° C. and a humidity of 10% for 1day. After that, printing was performed on high-quality dedicated paper(trade name: HR-101; manufactured by CANON Inc.) in the environmenthaving a temperature of 15° C. and a humidity of 10% by means of the inkwith a duty of 50%. Furthermore, printing was performed again in thesame manner as that described above after a certain time interval fromthe above printing, and the time interval after which remarkable lack ordot mis-alignment occurred at an early stage of printing was measured.Start up ejection stability was evaluated by means of the measured timeon the basis of the following criteria. Table 7 shows the results.

A An intermission of 5 seconds or longer

B An intermission of 3 seconds or longer and shorter than 5 seconds

C An intermission of shorter than 3 seconds TABLE 7 Example ComparativeExample 1 2 3 4 5 6 7 1 2 3 4 Yellow Ink A B C D E F G H I J K X[mass %](*4) 28.2 26.2 28.2 26.2 26.2 20.0 28.6 32.2 19.0 28.2 30.5 Y[mass %](*5) 19.2 19.2 19.2 13.2 13.2 10.0 18.6 15.2  9.0 19.2 15.0 Z[%] (*6)68.1 73.3 68.1 50.4 50.4 50.0 65.0 47.2 47.4 68.1 49.2 Humidity A A A BB B A C C D C resistance Intermittent A B B A B B B A A A B ejectionstability(*4) The total content of water-soluble organic solvents [mass %](*5) The content of a water-soluble organic solvent satisfying theexpression (2) [mass %](*6) A ratio of the water-soluble organic solvent satisfying theexpression (2) to the total content of the water-soluble organicsolvents (%)

As can be seen from Table 7 above, when Examples 1 to 7 are comparedwith Comparative Examples 1, 2, and 4, excellent humidity resistance isobtained in the case where Exemplified Compound 1 having a colordifference (ΔE) judged by means of the method of judging properties of acoloring material of 9 or less is used and the content of awater-soluble organic solvent satisfying the relationship represented bythe expression (2) with respect to the total content of thewater-soluble organic solvents in the ink is 50 mass % or more. WhenExamples 1, 2, 3, and 7 are compared with Examples 4, 5, and 6,additionally excellent humidity resistance is obtained in the case wherethe content of the water-soluble organic solvent satisfying therelationship represented by the expression (2) with respect to the totalcontent of the water-soluble organic solvents in the ink is 65% or more.When Example 1 is compared with Example 3, humidity resistance andexcellent start up ejection stability are obtained in the case whereethylene urea is incorporated as the water-soluble organic solventsatisfying the relationship represented by the expression (2). WhenExample 4 is compared with Example 5, humidity resistance and excellentstart up ejection stability are obtained in the case where any one ofdiethylene glycol, 2-pyrrolidone, and ethylene urea is incorporated asthe water-soluble organic solvent satisfying the relationshiprepresented by the expression (2).

<Judgment of Humidity Resistance of Coloring Material>

The humidity resistance of each of various coloring materials was judgedby means of the following method. Hereinafter, a specific example of amethod of judging humidity resistance will be described.

(Preparation of Model Ink and Clear Ink)

To be specific, a model ink was prepared according to the followingcomposition by using glycerin and urea as water-soluble organicsolvents, Acetylenol E100 (manufactured by Kawaken Fine Chemicals Co.,Ltd.) as a surfactant, and C.I. Direct Yellow 132 as a coloringmaterial. Glycerin  10 mass % Urea  10 mass % Acetylenol E100(manufactured by Kawaken Fine 1.0 mass % Chemicals Co., Ltd.) C.I.Direct Yellow 132 3.0 mass % Water Balance

Next, separately from the model ink, a clear ink was prepared byreplacing the coloring material portion of the model ink with water.

Water has an evaporation rate of 100%. Meanwhile, glycerin and urea usedhere as water-soluble organic solvents have evaporation rates X (mass %)of 0 mass % and 0.1 mass %, respectively. In addition, glycerin has amoisture absorptivity Y (mass %) of 66.9 mass % and urea has a moistureabsorptivity Y (mass %) of 86.0 mass %. Therefore, each of glycerin andurea corresponds to a water-soluble organic solvent having anevaporation rate X (mass %) smaller than that of water and a moistureabsorptivity Y (mass %) of 20 or more.

(Printing by Means of Model Ink and Clear Ink)

An ink jet printer (trade name: PIXUS 950i; manufactured by CANON Inc.)and a recording medium (trade name: SP-101; manufactured by CANON Inc.)were used for creating an image for evaluation. An image with a totalduty of 80% in which the above model ink with a printing duty of 10% andthe above clear ink with a printing duty of 70% were superimposed wasprinted in an environment having a temperature of 25° C. and a humidityof 60%.

(Leaving of Recorded Article)

The recorded article was left in the environment having a temperature of25° C. and a humidity of 60% for 48 hours. After that, the CIE-Labvalues of the image were measured by means of a spectrophotometer (tradename: Spectrolino; manufactured by Gretag Macbeth), and the values ofLab=(L₁, a₁, b₁) in the CIE-La*b* color space in an initial standardstate were determined. At that time, L₁=93.6, a₁=−7.5, and b₁=36.8.

After that, the recorded article was left in an environment having atemperature of 30° C. and a humidity of 80% for 168 hours, and then theCIE-Lab values of the image were measured by means of aspectrophotometer (trade name: Spectrolino; manufactured by GretagMacbeth), and the values of Lab=(L₂, A₂, B₂) in the CIE-La*b* colorspace in an initial standard state were determined. At that time,L₂=93.5, a₂=−9.6, and b₂=45.0. The results confirmed the followingexpression.ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}=8.5   (1)

The color difference (ΔE) between any other coloring material before theleaving in the environment having a temperature of 30° C. and a humidityof 80% and the coloring material after the leaving in the sameenvironment is as shown in Table 8 below. TABLE 8 Maximum value of ΔEobtained by means of a method of Coloring material judging humidityresistance Yellow coloring material Y1 7.5 Direct Yellow 132 8.5 DirectYellow 142 8.0 Direct Yellow 86 5.0 Direct Yellow 173 4.8 Acid Yellow 239.7

<Preparation of Ink>

Inks L to U of Examples and inks V to Y of Comparative Examples wereprepared by means of Exemplified Compound 1 thus prepared and therespective coloring materials, according to the prescription shown inTable 9. TABLE 9 Ink L M N O P Q R S T U V W X Y Exemplified 0.5 1.0 0.50.5 0.5 0.5 0.5 0.5 0.5 3.0 0.5 0.5 0.5 0.5 Compound 1 C.I.Direct 2.53.0 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 Yellow 132 C.I.Direct 3.0 Yellow 142C.I.Direct 3.0 Yellow 86 C.I.Direct 0.5 Yellow 173 C.I.Acid 2.5 Yellow23 Ethylene 4.2 11.2 3.0 10.0 glycol Diethylene 9.2 9.2 9.2 5.0 5.0 9.29.2 9.2 9.2 9.2 glycol 2- 5.0 5.0 5.0 2.0 5.0 9.4 5.0 5.0 5.0 5.0 5.05.0 pyrrolidone Ethylene 5.0 5.0 3.0 3.0 5.0 5.0 5.0 5.0 urea 1,5- 5.0pentanediol N-methyl-2- 4.0 pyrrolidone Butyl 2.0 carbitol Isopropyl 3.0alcohol Urea 5.0 10.0 5.0 10.0 Glycerin 9.0 7.0 9.0 12.0 12.0 10.0 10.09.0 9.0 9.0 13.0 5.0 9.0 5.5 Polyethylene glycol (*1) Surfynol 0.1104PG50 (*3) Ion- 67.9 68.9 67.9 69.9 69.9 76.1 67.5 67.4 67.4 62.4 65.177.9 67.9 65.6 exchanged water(*2) Ethylene oxide adduct of acetylene glycol (surfactant)(*3) (Surfactant; manufactured by Nissin Chemical Industry Co., Ltd.)

<Printing Evaluation>

Clear inks L to Y were prepared by replacing each of the coloringmaterials in the prescription of the inks L to U of Examples and theinks V to Y of Comparative Examples thus obtained with pure water. Anink jet printer (trade name: PIXUS 950i; manufactured by CANON Inc.) wasused for the evaluation.

(1) Humidity Resistance of Ink

Each of the inks of Examples and Comparative Examples was changed in theduty range of 0% to 100% in an increment of 5% and the correspondingclear ink was changed in the duty range of 0% to 100% in an increment of5% to create an image for evaluation having a superimposed gradationpattern. The combination of the ink and the clear ink was thecombination of the ink L and the clear ink L, the combination of the inkM and the clear ink M, or the like. A glossy recording medium (SP-101;manufactured by CANON Inc.) was used as a recording medium. Theresultant recorded article was left in an environment having atemperature of 25° C. and a humidity of 60% for 48 hours, and then thecolor tone of the superimposed gradation pattern portion was measured bymeans of a spectrophotometer (trade name: Spectrorino; manufactured byGretag Macbeth). The recorded article was additionally left in anenvironment having a temperature of 30° C. and a humidity of 80% for 168hours, and then the color tone was measured in the same manner as thatdescribed above by means of the spectrophotometer as that describedabove. The color difference (ΔE) in each image for evaluation wascalculated on the basis of the following expression (1) from the colortone of the image for evaluation after having been left in theenvironment having a temperature of 25° C. and a humidity of 60% for 48hours and the color tone of the image for evaluation after having beenleft in the environment having a temperature of 30° C. and a humidity of80% for 168 hours.

Values of La*b* in the CIE-La*b* color space of the image for evaluationafter having been left in the environment having a temperature of 25° C.and a humidity of 60% for 48 hours (initial standard state)=(L₁, a₁, b₁)

Values of La*b* in the CIE-La*b* color space of the image for evaluationafter having been left in the environment having a temperature of 30° C.and a humidity of 80% for 168 hours (after an acceleration test)=(L₂,a₂, b₂)ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}  (1)

The maximum color difference (ΔE) out of the color differences in therespective images for evaluation calculated on the basis of theexpression (1) was calculated, and each ink was evaluated for humidityresistance on the basis of the following criteria. Table 9 shows theresults.

A 4.0≧ΔE

B 5.5≧ΔE>4.0

C 7.0≧ΔE>5.5

D ΔE>7.0

(2) Start up Ejection Stability

An ink jet printer on which an ink cartridge storing each of the inks ofExamples and Comparative Examples had been mounted was left in anenvironment having a temperature of 15° C. and a humidity of 10% for 1day. After that, printing was performed on high-quality dedicated paper(HR-101; manufactured by CANON Inc.) in the environment having atemperature of 15° C. and a humidity of 10% by means of the ink with aduty of 50%. Furthermore, printing was performed again in the samemanner as that described above after a certain time interval from theabove printing, and the time interval after which remarkable lack or dotmis-alignment occurred at an early stage of printing was measured. Startup ejection stability was evaluated by means of the measured time on thebasis of the following criteria. Table 9 shows the results.

A An intermission of 5 seconds or longer

B An intermission of 3 seconds or longer and shorter than 5 seconds

C An intermission of shorter than 3 seconds

(3) Image Density

Each of the inks of Examples and Comparative Examples was used toperform printing with a duty of 100%, to thereby produce a recordedarticle. A glossy recording medium (SP-101; manufactured by CANON Inc.)was used as a recording medium. The resultant recorded article wasnaturally dried for 24 hours. The optical density of a printed portionwas measured by means of a spectrophotometer (trade name: Spectrolino;manufactured by Gretag Macbeth), and an image density was evaluated onthe basis of the following criteria. Table 9 shows the results.

A An optical density of larger than 1.85

B An optical density of 1.75 or more and 1.85 or less

C An optical density of smaller than 1.75

(4) Color Tone

Each of the inks of Examples and Comparative Examples was used toperform printing with a duty of 100%, to thereby produce a recordedarticle. A glossy recording medium (PR-101; manufactured by CANON Inc.)was used as a recording medium. The resultant recorded article wasnaturally dried for 24 hours. The chroma (C) and hue angle (h) of aprinted portion were measured by means of a spectrophotometer (tradename: Spectrolino; manufactured by Gretag Macbeth). The chroma (C) wascalculated on the basis of the following expression (3) from the valuesof a*b* in the CIE-La*b* color space. The chroma and the hue angle wereevaluated on the basis of the following criteria. Table 10 shows theresults.C=√{square root over (a ² +b ² )}  (3)

Chroma (C)

A C of 105 or more

B C of 95 or more and less than 105 Hue angle (h)

A h is 85 or more and less than 90.

B h is 83 or more and 85 or less, or is 90 or more and 92 or less.

C h is less than 83, or is larger than 92. TABLE 10 Example ComparativeExample 8 9 10 11 12 13 14 15 16 17 5 6 7 8

nk L M N O P Q R S T U V W X Y

[mass %] (*4) 28.2 26.2 28.2 26.2 26.2 20.0 28.6 28.2 28.2 33.2 31.019.0 28.2 30.5

[mass %] (*5) 19.2 19.2 19.2 14.2 14.2 10.0 18.6 19.2 19.2 19.2  8.0 9.0 19.2 15.0

[%] (*6) 68.1 73.3 68.1 54.2 54.2 50.0 65.0 68.1 68.1 57.8 25.8 47.468.1 49.2

umidity A A A B B B A B A B D C C C

esistance

ntermittent A B B A B B B B B B A A B B

jection

tability

mage A A A A A A A B A B A A C A

ensity

hroma (C) A A A A A A A A A B A A A A

ue angle A A A A A A A B C B A A B A

h)(*4) The total content of water-soluble organic solvents [mass %](*5) The content of a water-soluble organic solvent satisfying theexpression (2) [mass %](*6) A ratio of the water-soluble organic solvent satisfying theexpression (2) to the total content of the water-soluble organicsolvents [%]

As can be seen from Table 10 above, when Examples 8 to 17 are comparedwith Comparative Examples 5, 6, and 8, excellent humidity resistance isobtained in the case where the content of a water-soluble organicsolvent satisfying the relationship represented by the expression (2)with respect to the total content of the water-soluble organic solventsin the ink is 50 mass % or more. When Examples 8, 9, 10, and 14, andExamples 11, 12, and 13, which involve the use of the same coloringmaterial, are compared, additionally excellent humidity resistance isobtained in the case where the content of the water-soluble-organicsolvent satisfying the relationship represented by the expression (2)with respect to the total content of the water-soluble organic solventsin the ink is 65% or more. When Examples 8 to 14 are compared withExamples 15 to 17, with regard to an image density and a color tone,excellent humidity resistance, excellent start up ejection stability, anexcellent image density, and an excellent color tone are obtained byusing Exemplified Compound 1 and C.I. Direct Yellow 132 in combination.When Example 8 is compared with Example 10, humidity resistance andexcellent start up ejection stability are obtained in the case whereethylene urea is incorporated as the water-soluble organic solventsatisfying the relationship represented by the expression (2). WhenExample 11 is compared with Example 12, humidity resistance andexcellent start up ejection stability are obtained in the case where anyone of diethylene glycol, 2-pyrrolidone, and ethylene urea isincorporated as the water-soluble organic solvent satisfying therelationship represented by the expression (2).

The present application claims the priority from each of Japanese PatentApplication No. 2004-196446 filed on Jul. 2, 2004, Japanese PatentApplication No. 2004-196449 filed on Jul. 2, 2004, and Japanese PatentApplication No. 2005-193806 filed on Jul. 1, 2005, the contents of whichare cited to constitute part of the present application.

1. An ink jet ink, comprising at least a coloring material andwater-soluble organic solvent, characterized in that the ink jet inksatisfies the following conditions (A) and (B): (A) A color differenceΔE judged by means of a method of judging properties of a coloringmaterial including the following steps (1) to (3) is 9 or less, (1) Astep involving: applying a model ink comprising the coloring material,water, and a water-soluble organic solvent having an evaporation rate X(mass %) smaller than the evaporation rate of water and a moistureabsorptivity Y (mass %) which is 20 or more and satisfies a relationshipof Y≧2.8X+10; and applying a clear ink prepared by replacing only thecoloring material of the model ink with water on the model ink in such amanner that an amount of the model ink is smaller than that of the clearink, (2) A step involving: leaving a recorded article obtained in thestep (1) in an environment having a temperature of 25° C. and a humidityof 60% for 48 hours; and subsequently leaving the recorded article in anenvironment having a temperature of 30° C. and a humidity of 80% for 168hours, (3) A step of judging the color difference (ΔE) represented bythe following expression (1) between the recorded article before theleaving for 168 hours and the recorded article after the leaving for 168hours,ΔE=√{square root over ((L ₁-L ₂)²+(a ₁-a ₂)²+(b ₁-b ₂)²)}  (1) (In theexpression (1), L₁, a₁, and b₁ represent L, a, and b of an Labcolorimetric system after the leaving for 48 hours and before theleaving for 168 hours, respectively, and L₂, a₂, and b₂ represent L, a,and b of the Lab calorimetric system after the leaving for 168 hours,respectively.) (B) A content of a water-soluble organic solvent in whichthe evaporation rate X (mass %) and the moisture absorptivity Y (mass %)satisfy a relationship represented by the following expression (2) inall the water-soluble organic solvents in the ink is 50 mass % or more.Y≦2.8X+10  (2) (In the expression (2), X represents an evaporation rateand Y represents a moisture absorptivity.)
 2. An ink jet ink accordingto claim 1, wherein the number of the coloring material is at least two;and each of the coloring materials satisfies the conditions (A) and (B).3. An ink jet ink according to claim 1, wherein the content of thewater-soluble organic solvent satisfying the expression (2) is 65 mass %or more with respect to a content of all the water-soluble organicsolvents in the ink.
 4. An ink jet ink according to claim 1, wherein thecoloring material comprises a compound represented by the followinggeneral formula (I) or a salt thereof;

wherein M's each independently represent a hydrogen atom, an alkalimetal, an alkali earth metal, a cation of organic amine or an ammoniumion, and n's each independently represent 1 or
 2. 5. An ink jet inkaccording to claim 1, wherein the water-soluble organic solventsatisfying the expression (2) is selected from the group consisting ofethylene glycol, diethylene glycol, 2-pyrrolidone, 1,5-pentanediol,1,6-hexanediol, and ethylene urea.
 6. An ink jet ink according to claim5, wherein the water-soluble organic solvent satisfying the expression(2) comprises diethylene glycol, 2-pyrrolidone, or ethylene urea.
 7. Anink jet ink, comprising at least a coloring material and water-solubleorganic solvent, characterized in that the ink jet ink satisfies thefollowing conditions (A) and (B): (A) The ink jet ink contains acompound represented by the following general formula (I) or a saltthereof, (B) A content of a water-soluble organic solvent in which anevaporation rate X (mass %) and a moisture absorptivity Y (mass %)satisfy a relationship represented by the following expression (2) inall the water-soluble organic solvents in the ink is 50 mass % or more,

wherein M's each independently represent a hydrogen atom, an alkalimetal, an alkali earth metal, a cation of organic amine or an ammoniumion, and n's each independently represent 1 or 2.Y≦2.8X+10  (2) (In the expression (2), X represents an evaporation rateand Y represents a moisture absorptivity.)
 8. An ink jet ink accordingto claim 7, further comprising C.I. Direct Yellow 132 as the coloringmaterial.
 9. An ink jet ink according to claim 7, wherein the content ofthe water-soluble organic solvent satisfying the expression (2) is 65mass % or more with respect to a content of all the water-solubleorganic solvents in the ink.
 10. An ink jet ink according to claim 7,wherein the water-soluble organic solvent satisfying the expression (2)is selected from the group consisting of ethylene glycol, diethyleneglycol, 2-pyrrolidone, 1,5-pentanediol, 1,6-hexanediol, and ethyleneurea.
 11. An ink jet ink according to claim 10, wherein thewater-soluble organic solvent satisfying the expression (2) comprisesdiethylene glycol, 2-pyrrolidone, or ethylene urea.
 12. An ink jet ink,comprising at least a coloring material and a water-soluble organicsolvent, characterized in that: the coloring material comprises acompound represented by the following general formula (I) or a saltthereof; and the water-soluble organic solvent is selected from thegroup consisting of ethylene glycol, diethylene glycol, 2-pyrrolidone,1,5-pentanediol, 1,6-hexanediol, and ethylene urea:

wherein M's each independently represent a hydrogen atom, an alkalimetal, an alkali earth metal, a cation of organic amine or an ammoniumion, and n's each independently represent 1 or
 2. 13. An ink jet inkaccording to claim 12, further comprising C.I. Direct Yellow 132 as thecoloring material.
 14. An ink jet ink according to claim 12, wherein acontent of the water-soluble organic solvent is 65 mass % or more withrespect to a content of all water-soluble organic solvents in the ink.15. An ink jet ink according to claim 12, wherein the water-solubleorganic solvent comprises diethylene glycol, 2-pyrrolidone, or ethyleneurea.
 16. An ink jet recording method, comprising ejecting an ink by inkjet method, characterized in that the ink comprises the ink jet inkaccording to claim
 1. 17. An ink jet recording method, comprisingejecting an ink by ink jet method, characterized in that the inkcomprises the ink jet ink according to claim
 7. 18. An ink jet recordingmethod, comprising ejecting an ink by ink jet method, characterized inthat the ink comprises the ink jet ink according to claim
 12. 19. An inkcartridge, comprising an ink storage portion for storing ink,characterized in that the ink comprises the ink jet ink according toclaim
 1. 20. An ink cartridge, comprising an ink storage portion forstoring ink, characterized in that the ink comprises the ink jet inkaccording to claim
 7. 21. An ink cartridge, comprising an ink storageportion for storing ink, characterized in that the ink comprises the inkjet ink according to claim
 12. 22. A recording unit, comprising an inkstorage portion for storing ink and a recording head for ejecting theink, characterized in that the ink comprises the ink jet ink accordingto claim
 1. 23. A recording unit, comprising an ink storage portion forstoring ink and a recording head for ejecting the ink, characterized inthat the ink comprises the ink jet ink according to claim
 7. 24. Arecording unit, comprising an ink storage portion for storing ink and arecording head for ejecting the ink, characterized in that the inkcomprises the ink jet ink according to claim
 12. 25. An ink jetrecording apparatus, comprising an ink storage portion for storing inkand a recording head for ejecting the ink, characterized in that the inkcomprises the ink jet ink according to claim
 1. 26. An ink jet recordingapparatus, comprising an ink storage portion for storing ink and arecording head for ejecting the ink, characterized in that the inkcomprises the ink jet ink according to claim
 7. 27. An ink jet recordingapparatus, comprising an ink storage portion for storing ink and arecording head for ejecting the ink, characterized in that the inkcomprises the ink jet ink according to claim 12.